The invention relates to a drill fit for carrying out wide diameter and high depth holes, especially for pilings and wells, and method for carrying out thereof.
Document U.S. Pat. No. 2,910,274 discloses a drill for digging holes for pouring bell-shaped footings having a motor rigidly fixed to the lower and of an upper column member. The motor is connected by means of pinions to a lower column member and axially rotates the lower column member with respect to the upper column member.
The drill includes an hydraulic fed linked to the motor. The whole column assembly, including column members and motor, is shifted vertically by means of a cable wound up on a reel of a crane and fixed to an arm of a boom engaging pulleys associated to the rigid connection between motor and upper column member.
A carrier canister is fixed to the lower and of the lower column member and has, at list at its free and, a digging tool. A support assembly of the canister reciprocates along lower column member, by means of an hydraulic actuator, to open and close the carrier canister.
The main drawbacks of this known drill consist in that, because of the column members, it cannot carry out high depth holes and, because or the fixed connection between the canister and the lower and of the lower column member, the digging phase must be stopped in correspondence of the descending, unloading and lifting of the canister.
The piles for the soil consolidation are commonly realized during the drilling phase, the reinforcement bar installation and concrete casting. The drillings are carried out by means of soil cutting or crumbling and carrying away the removed material.
Currently the material removing is done by means of either intermittent transport, using hammer grabs or a telescopic Kelly driven by a rotary, that must be lifted each time, or continuous transport by means of a cochlea or by fluid circulation.
The hammer grab utilization is limited to the scarce cohesion grounds, particularly to transport material trough the casing pipes.
Using the rotary with telescopic Kelly system is possible to make holes for wide diameter piles (up to 2-3 meters) but for limited depth, typically 50-60 m. The depth limit is due to the fact that the cutting and material transport tool is linked to the inferior end of series of telescopic stem fit to transmit the cutting torque. With the hole depth increasing, the stem length or the number of the used clements must increase with difficulties imposing the cited limits.
Increasing the diameter, the resistance of said elements must be also increased. So the wide diameter and high depth holes can be obtained only with very high, heavy and expensive machines that sometimes don""t have the required space to operate.
With the cochlea system, it is used an helix with the sharp tools in the inferior part, linked in the upper part to a rotary that drive the rotating movement and to extraction wire ropes. Said method requires high extraction forces and very high machines, whose height is comparable to the hole depth. Practically holes with 1,2-1,5 m as maximum diameter and 25-30 m as maximum depth are possible.
The circulating fluid systems require water pumps, or air compressors with flows growing with the diameter and depth increasing. Said systems allow to reach very high depth only if the working diameters are small (200-300 mm). Wider diameter holes (800-1400 mm) would be done using great flow rates required to the crumbled material lifting.
The reverse circulation system allows to drill deep and large diameter holes lifting the cut or crumbled material in a stream of water moved upward inside the stem by compressed air. This system can be used only in waterproof soil, or on the sea or lakes or making the hole waterproof thanks to expensive casings.
An object of the present invention is to allow the carrying out of great diameter and high depth holes, for pilings or wells with an equipment limited in height, weight and cost, usable also under bridges, tunnels, buildings near electric cables, in lakes and in the sea.
Another object is to hardly increase the hole execution speed.
According to the method and the machine of the present invention, the drilled material is carried to the surface by a carrier canister or similar that slides along the drill stems rotated by a rotary, being linked to ropes moved by winches rotating integral with the stems. So the material can be quickly and continuously removed, without lifting and moving the stems and without necessarily stopping the drilling operations.
The above described objects are obtained in accordance with the content of the claims.